Concrete form lining and method of manufacture



E. FREDERICK, JR., ETAI. 2,432,002

CONCRETE FORM LINING ANDa METHOD OF MANUFACTURE Filed oct. 2o, 19'41 a@ #572276@ fffjaz.

I Patented Dec. 1947 CONCRETEOFORM lace Waterfall, Chicago, Ill

s PATENT OFFICE LINING` AND METHOD F MANUFACTUBE Emile Frederick, Jr., New Orleans, La., and Walassignorato The Celotex Corporation, Chicago, lll., a corporation oi Delaware Application October 20, 1941-, Serial No. 415,754

l The linvention hereof relates to a new and improved method of concrete construction, including'as an essential feature thereof the use of a new and improved v,concrete form lining maiterial and the manufacture thereof, and in connection with which there result concrete structures having, in particular, surfaces greatly improved as compared with those vobtained in the practice of current methods of concrete. construction.

In the erection of concrete structures, whether dams, buildings, bridges or the like, it is cornmon practice to provide Vforms in which the concrete is applied, which forms, after the concrete is set, are removed leaving the structure formed or molded in accordance with the contour of the forms. This also applies to the manufacture of concrete blocks, slabs, and the like wherein such products are molded in molds which constitute forms and in which vlikewise the contour is dependent upon the contour of. the form or mol in which such products are cast.

According to common practice, the forms which are used in connection with concrete construction are composed of metal, matched lum# ber, rough lumber, plywood,l'ard and dense ber board, known as hardboard, or any other generally like or similar materials or of variouscombinations thereof. The such materials are suitably supported so that the concrete may be cast thereagainst. For some' structures the concrete face as it is molded by the usual forms is satis# factory, as for example, in foundation work where the face of the concrete will be covered by a back lill, or in connection with a surface which will be covered, as for example, by application of a veneer facing of brick or stone and the like.

For many purposes the usual face produced on concrete cast against forms as above mentioned is not satisfactory, since such faces have various common defects, as for example, they may show the wood grain markings of the wood forms or may show the joint lines between the boards of the form lining, or the surface may be honeycombed or pitted. The Aface of such concrete forms are usually oiled to prevent adhesion 16 Claims. (Cl. 15de-45.9)

- It is in particular an object of this invention to provide an improved face on concrete structures, which face will be more dense than that obtained by following present practices, will be smooth or uniformly and lightly textured and substantially without the detrimental imperfections and disgurements heretofore usual as above mentioned. In connection with producing the desired results, it is an object of this invention to provide an improved method of concrete construction, and in particular to provide a new and improved form lining material which is utiliz'ed in erecting or preparing the improved concrete structure which is obtained by the practice of the method of this invention.

In connection with the new and improved form lining hereof, the objects to be achieved by the use thereof are the provision of such material in large sheets so as to minimize joint markings on the concrete cast thereagainst, so that in the finished structure there are relatively few joint marks which, if the adjacent sheets of form 1ining have been properly placed, will be substantlally unnoticeable and which said large sheets are used in concrete forms without the necessity of oiling or otherwise treating on the .lob before using. A further object is to provide the new and improved form lining hereof having a uniform surface of smooth or textured -appearance so as to provide ya similar uniform surface on concrete cast against it. A still further object hereof is to cause the concrete cast against the form lining hereofto have a hardandldense surface, free, or substantially free, of air pockets or honeycomb, and for accomplishing these ends to provide such a form lining which has the properties of affording escape of trapped air from the surface of the concrete cast thereagainst, and of providing for the escape of air and water from the such face.

With the above and other objects of the in' vention hereof in view, the following, as will be apparent upon reading the specification, is a description of the invention hereof and the appended claims deiinethe invention set out in the specification.

The invention hereof is illustrated insofar as is practical in the accompanying drawings. In the drawings in which like numerals designate like elements in the various views;

Figure 1 is a perspective of a concrete wall or the like showing the concrete form on one side thereof with the form lining in place, parts thereof being broken away;

Figure 2 is a diagrammatic perspective of the form lining material: and

Figure 3 is a diagrammatic perspective of a modication of the form lining material illustrated in Figure 2.

In the drawings, in Figure 1 there is illustrated a typical concrete wall I0, a form lining material il against which a face of the Wall is cast, supporting form boards l2 and framing I3 to which the form boards i2 are secured by nails or bolts or other suitable securing means, not shown.

'I'he construction shown in Figure 1, itis to be understood, is merely illustrative, being an illustration for the purpose of description only. In practice of course, the wall I may in its entirety or with respect to its face portion only be inclined from the vertical or instead of being ilat may be curved or it may represent merely a part of a massive structure such as a dam or the like having a face which is straight or inclined or at or curved or the like, or it may be considered as representing a' portion of a concrete block or slab or the like.

In utilizing and carrying out the invention hereof, the only departure from the usual and ordinary practices in concrete construction is in the inclusion of an absorptive form lining in the concrete forms. This absorptive form lining, indicated in the drawings by numeral il, is an especially treated sheet of ber board, more specically an especially treated sheet of ber insulation board, which is placed in the form as a face against which the concrete is to be cast. The form lining is suitably secured to the face of the form boards I2 by suitable nailing. not shown, preferably using small headed nails such as lath nails spaced 4 to 6 inches along the edges and 12 inches or more on center portions, or if desired, it may be suitably adhered with a latex or casein or other preferably waterproof adhesive.

The basis of the form lining is ber board, in fact ber insulation board of the nature of that now commonly available under a number of brand names, but however, the board found most satisfactory is that available as Celotex brand cane ber insulation board. Other ber insulation boards may be utilized in connection with this invention, as for example, Insuliie brand ber insulation board, which is composed largely of ground wood, or Maftex brand ber insulation board, which is composed principally of the ber of the roots from which licorice is extracted, or in fact there may be utilized, as will become apparent, substantially any of the commercially available ber insulation boards.` These ber insulation boards as generally available for use in building construction have a density of about 0.25 to 0.27, and while the regular commercial ber boards maybe used, it is preferable in the exercise of the invention hereof that a slightly less dense ber board be used, that is, a board of the same character as those mentioned, but of a density of about 0.210 to 0.220 prior to subsequent surfacing treatments.

These ber insulation boards are sheet form products manufactured from vegetative bers, the larger portion of the bers being relatively coarse as compared to usual paper ber but with a content of ner ber produced most generally in 1/2 inch thickness, as sheets 4 feet wide and in length up to 12 feet or longer. yA common characteristic of these ber insulation boards is that in their usual commercial form, sold for wall,

structural insulation, they have a conductivity of approximately 0.33.

In the drawings, a sheet of ber insulation board is designated generally by numeral I5, Fig. 2. In the usual process of the manufacture of ber insulation board, the bers are waterproofed, that is they are treated with a so-called paper size, as for example, with rosin emulsion, which is subsequently precipitated on the bers by the addition of paper makers alum. The procedure of sizing with rosin and alum and other waterproong sizings such as asphalt, waxes and other sizing agents being well known to those skilled in the paper art and ber insulation board industry, a detailed description thereof will not be given here, it being considered suiilcient to state that preferably, in connection with the invention hereof, the ber insulation board comprising the base material for the form lining shall be a ber insulation board which has been suitably integrally sized or waterproofed.

The sizing of ber, as with rosin and alum, for example, provides on the surface of the individual bers a more or less complete but discontinuous coating of what is believed to be aluminum resinate and free rosin deposited on the surface of the sized bers. This coating has a high surface tension and therefore resists wetting by water, so that the bers and products formed therefrom are waterproofed or, possibly more properly stated, are water repellent due to the high surface tension of the sizing on the surface of the bers.

Starting with a sized ber insulation board sheet, preferably of a density as previously stated of about 0.210 to 0.220, the bers of which are 'relatively large and coarse as compared with paper ber so that in fact, in general, it may be said that in excess of 50% of its volume constitutes voids or interstices between bers, and having a surface which is relatively open and porous when viewed under magnification of four diameters; the preparation of the sheet as a form lining is as follows:

'I'he ber board sheet I5, a sized sheet and one which is relatively porous to air, from a surface thereof in accordance with a method of determination which will be set out below, is treated as will be hereafter described in detail with a surface tension depressant.

The method for determining the required porosity above referred to is a slight modication of the method usually used for determining the porosity or air permeability of roong felts, that is, the unsaturated sheet which is the basis of asphalt saturated roong products, and the method involves the use of the Gurley densometer. Neither the apparatus used for the determination of air permeability, nor the method of use thereof will be described in detail, since this is covered in tentative specication D202-32T of the American Society for Testing materials. However, since the detailed procedure of testing in connection with the preparation of the concrete form lining hereof differs slightly from the standard and requires a slight modication of the apparatus these differences will be described.

The standard procedure as covered in the above tentative specication is modified to the extent that the sample tested is a simple of the ber insulation board which is to be treated, which sample is cut one and seven-eighths inch square and sanded to a thickness of 0.3 inch. By using such a `test piece the standard apparatus may be used but it will be understood that asimilar apparatus could be built in which the test could be made on a sample of larger area and of full thickness. the extent that this described sample used for testing is clamped down on the apparatus with one-fourth inch stops, provided so that rm contact of the sample is obtained and the test is made on a sample which is exactly one-fourth inch thick as limited by the stops and which is tested in a state of slight compression, i. e., from .30" to .25". The ber board to be used in connection with the preparation of the form lining board hereof should be a fiber board sheetas above described, which when tested in accordance with the testing procedure of tentative specification D202-32T shows an air resistance of around 3 to 4 seconds per 100 cc., although a reasonable variation from these figures may be compensated n for in the course of the subsequent steps of prepa-- ration of the form lining board.

' Preferably, the test fordetermining the porosity of the ber board sheet in accordance with` the above test procedure should be made on what vis termed the bottom side of the sheet, that is, the side which is felted on the screen in the manufacture of the fiber board. 'Ihis bottom side of the sheet is, due to the manner of manufacture The testing apparatus is modified to of the fiber board, ordinarily somewhat smoother l than the top side of the sheet and due to the effect of drainage during the felting of the sheet the bottom side of the sheet is generally somewhat more open than the top side,'that is, the drainarge of the water from the sheet as it is formed y side of the sheet,

including the use of the form lining board.l

While the starting board has been described as preferably having a density of 0.210 to 0.220 .and an air resistance of 3 to 4 sec. this is not always necessary and depends upon the treatment which will be employed. Boards which are to be lightly treated may have a starting density in excess of 0.220 and an air resistance in excess of 4 seconds per 100 cc.

Since in connection with this invention and the utilization thereof it is desired that the advantages of two directly opposed conditions be taken advantage of, there will now be described these conditions and the manner in which they are utilized. The fiber insulating board suitably sized, as has been described, is waterproofed or water repellent so that its tendency is to repel water rather than to absorb water which might be in contact therewith. In connection with the concrete which is cast against the form lining, it is desired to remove from the surface of such concrete all excess moisture by absorption of this moisture into the fiber board form lining. Since as stated, the ber board form lining is water repellent, in orde;` that the water may be absorbed from the concrete, it is necessary that a surface of the fiber board form lining be given a treatment to render it water absorptive, which treatment will be hereinafter described.

It is desired that a waterproof repellent fiber board form lining shall be used since, if not sized,

ilabby. Ifthere ls used for the form lining a ber board which was not waterproofed, upon the removal of the forms there wouldgpossiblybe considerable diiliculty encountered `in removing the fiber board form lining. Not being waterproofed, the entire form lining board would absorb water from the concrete cast against vits face, and it would be merely a board form, but pulpy mass lying on the face of the concrete, which pulpy material would be very difficult to remove. In stating4 that the form lining board under these conditions would be a pulpy mass it is not vmeant that it loosesl its form, butwith respect to its original condition when dry, more or less corresponding for example to a piece of ordinary cardboard which had been well wetted. The board will have lost a large part of its coherence, and literally speaking, it would be necessary to removeit from the surface with a shovel or possibly wash it ol with a water hose. By using a form liner board which is inherently waterproofed or water repellent, at least with respect to a considerable portion of the body thereof, this Waterproofed portion absorbs little or none of the water from the concrete cast-'against a face, and when the forms are removed it is possible to remove the form lining from the face of the concrete as an integral board. If carefully removed the used board will have some salvage value either for reuse as form liner or other utilization.

So thatthe ber insulation board, which as above stated should preferably be water repellent in order that it may retain its integrity for use as a concrete form lining, may be suitable for use ln connection with the inventions hereof it is necessary that a portion thereof from a face inwardly be suitably treated so that it will be water absorbent rather than water repellent. Whereas it has been stated that preferably the bottom side of the sheet is subjected to further treatment, it may be that in some instances it will be for reasons which will be described, preferable to treat the top side rather than the bottom side. The surface to be subjected to further treatment should be that surface Vwhich has an air porosity of the order as previously mentioned, that is, an air porosity of about 3 to 4 seconds per cc. when tested in accordance with the standard testing method as outlined. All fiber insulation boards do not maintain uniformity of their porosity, that is, there are differences in the particular fibers used by the various manufactures and further no manufacturer can' maintain absolute uniformity of the fiber used in the manufacture of ber insulation board. Due to this inherent variability, which results in variability of the air permeability it is preferable that the surface of board which has an air permeability of about 3 to 4 seconds shall'be that surface which is subjected to further treatment.

The further treatment to which the liber insulation board is subjected is a treatment for neutralizing or offsetting the waterproofing of the bers of the fiber board sheet, which treatment however is limited to the extent that it effects only one surface of the board, from a surface inwardly to a limited depth, about g1g but may be greater and preferably not exceeding onehalf of the thickness of the board.

One manner of subsequent treatment of the 7 used with equal ed'ect provided that in using such other surface tension depressant they are used in accordance with or in proportion to their relative effectiveness as surface tension depressants relative to sulphonated castor oil, that is, if the surface tension depressant effect of an alternative surface tension depressant is twice as great, then only one-half the amount shall Vbe used. A few of the numerous alternate surface tension depressants which may be used .are saponin or soap bark, sulfonated long chain alcohols. alkyl naphthalene sulfonate. or other of the numerous well known and commercially avail-A able types of wetting agents. v

When sulphonated castor oil is 'used as a wetting agent, it is preferably prepared for application as a 4% to 6% solution by volume as representing a suitable concentration for use. This solution is applied to that face of the fiber board selected in accordance with the foregoing explanation and may be applied in any given manner, as by spraying, roller coating or the like. On a board waterproofed with rosin and alum or other well known sizes, such as wax or rosin wax mixture and having an air porosity of approximately 3 to 4 seconds, the solution is applied at the rate of about 2 gallons per 1000 sq. ft. applied to one side only.

The amount of surface tension depressant solution applied as above, penetrates into the board from the surface to which it is applied to only a limited distance from the surface, in general to less than one-fourth of the thickness of the sheet when applied to a one-half inch sheet, that is. it penetrates to less than one-eighth inch. 'Ihe effect of this application of the wetting agent is to destroy in that part, the effectivenessof the size which was previously applied to the fibers, the surface tension is lowered and the portion of the board to which the wetting agent has been applied becomes readily wettable as compared to its previous condition of being water repellent. The remainder of the board into which the wetting agent does not penetrate remains waterproofed or water repellent so that ordinarily the board for three-fourths or more of its thickness is Water repellent with its other less'than one-fourth readily water absorptive. In the drawings, in Figure 2, it has been attempted to indicate the penetration of the wetting agent by light hatching lines, to which portion of the board there has been applied the numeral i6, that is, that portion i6 is the portion of the board, at and adjacent one surface which is water absorptive.

The water resistance of the treated surface after drying will have been decreased to such an extent that 1/2 cc. of water applied to the surface will be completely absorbed by the board in from 1 to 45 minutes instead of requiring a period of something like 10 hours or thereabouts which would be the normal absorption time of the l/gi cc. of water applied to the surface of a similar waterproof board, the surface of which had not been subjected to treatment with a surface tension reducing agent.

'Ihe board so treated with one surface having a l,/2 cc. absorption time of approximately l minute to 45 minutes and the remainder of the body of the board untreated, with an absorption time ofthe order of 10 hours may now be used as an effective absorptive form lining. A possible variation could be to have both surfaces of the board treated with the wetting agent so that either side can be used against the concrete and in such case the untreated core portion serves as a stiifening 8 and strengthening portion in the same manner as the untreated rear portion of the sheet as .lust previously described.

While boards treated as above described may be used as absorptive form lining without further treatment, the desired effects are obtained and concrete of a. superior nature results, the concrete surface produced may be slightly irregular and somewhat roughened due to irregularities of and coarseness of the surface of the treated sheet. Trouble may also be expected because of the concrete bonding to the surface fibers. When the form lining is removed some of the fibers at the surface of the sheet will most likely adhere to the face of the concrete. The form lining will be dimcult to remove as complete units and the concrete surface though fairly smooth and uniform may contain surface fibers strongly bonded toit, which are difllcult to remove and present an unsightly and undesirable appearance. This use will, however, not be described further herein as this phase of the general subject matter of the invention involved is considered to be a separate invention more properly to be separately described.

Bonding of the concrete to the form lining is considered to be due to the infiltration of wet cement fines from the concrete mixture into the surface pores of the form lining. Most fiber insulation boards which have been sized with rosin and alum have a pH value of 4.5 to 5.9 so that the setting time of the cement, which because carried along in the water which is absorbed from the concrete by the form lining, penetrates into the pores of the lining, is retarded by the acid condition encountered. If the form lining is removed at just the correct time, that is, just after the body of concrete has set but before the cement in the pores of the sheet has set, the lining may be stripped of! without sticking or bonding diiliculties.

This correct time for stripping as above stated however; is probably largely due to practical differences which on construction jobs are somewhat variable for different portions of the form lining, with the result that when the forms are removed, usually at about 24 hours from the time of pouring, some portions may'strip clean, whereas, other portions will be rather firmly bonded by the cement fines which have set up in the pores of the lining. If the forms are stripped in less than 24 hours less bonding trouble will be encountered. but the entire concrete surface will be coated with a thin powdery unset cement layer. This unset surface lm or layer is not necessarily objectionable as it will eventually set and harden, but in most cases stripping of the forms sooner than 24 hours after pouring is impractical. Where forms are not stripped for several days after the pouring, complete bonding over the entire surface 0f the lining will probably result and the lining can be removed only by scraping, scrubbing with water or by a combination of both. It is of course to be understood that the immediately foregoing statements are made with reference to the use of concrete embodying ordinary cement as distinguished from those in which is incorporated cegent of high early strength and rapid setting pes.

A further treatment involved in producing a form lining, the use of which will result in obtaining an improved hard and dense surface on concrete case thereagainst, together with such other treatments as have been above mentioned, is the application of a coating to a surface of the fiber board lining as will be described below. '1h18 treatment, is the application of a Surface coating on the fiber board lining surface to adhere the ilbers at the surface and strengthen the surface of the form lining, producing a surface which is not easily scuffed or marred intranslt or installation and -which has a high wet strength which promotes or facilitates stripping of the wet used f lining from the freshly set concrete. The applifrom the usual alkaline reactions of the cementqg and at the same time protect the cement from the deleterious residual acid character of the fiber board, particularly if sized with rosin and alum, and thereby permit maximum utilization of the fine layer of cement and aggregate which is screened out against the porous surface of the absorptive lining. i

In a/ber board to the surface of which there has ,been applied a properly designed surface treatment and which has also been treated'with a substantially neutral wetting agent the absorptive character'of the lining is not impaired, water and air are absorbed from the concrete, fine cement and aggregate are drawn to the surface and largely screened out on the surface of the lining. The form lining being non-acid in effect does not retard setting of the concentrated cement layer at the surface and hardening proceeds normally and rapidly up..y to the face of the form lining. When the form is removed after 24 hours or thereabouts the lining is strong enough to be pulled away from the set face, carrying with it only that small amount of fines which has actually penetrated into the form lining and leaving at the face of the concrete mass the rich hardened and desired surface effect. Also, due to the fact that the form lining absorbs from the concrete, particularly from its face and closely adjacent thereto, the occluded air and the excess water, the cement particles, atand closely adjacent the face are, prior to setting of the cement, in more intimate contact one with another than normally so that when `the cement does set the face resulting is of greater density and is harder than would be a similar face cast against the usual form linings.

' The surface treatment is diagrammatically shown in the drawings in `Figs. 2 and 3, indicated by numeral I'l, but it is to be distinctly understood that such showing in the drawings is but an attempt to show this surface treatment, and that this treatment is actually the treatment as will be immediately hereafter described.

In the drawing the surface coating I1 might appear to be on the surface of the ber board I5, but actually this treatment is really in the surface, that is, it is not a treatment which is merely applied over the surface, it is a treatment which is actually entirely, or almost entirely within a thin surface lamina of the ber board. As an example of thegsurface coating I1, it may comprise asphalt of preferably labout 180 F., M. P. applied at the rate of about 10 to 30 pounds per 1000 sq. feet of surface, this being applied as a substantially uniform coating by any desired means in any desired manner as by spraying, roller coating or the like.

The surface application of asphalt is made smoothed by hot rolling and the sheet is subsequently stoved or baked by suitable heating at about 250 to 350 F. until the asphalt coating is sufficiently softened to sink into the surface of ed sinks into the relatively open surface of the sheet to which it is applied. and due to its nature it tends to flow around or coat the individual surface fibers of the sheet so that as a-consequence of the limited amount of asphalt applied, it instead of being a continuous sheet on the surface, forms a relatively open and porous surfacing, at or in the surface, having fine pores or openings therethrough generally corresponding to the openings or pores which were present at the surface of the sheet between the bers of which the sheet is composed.

The treatment of the surface of the board not only forms the finely porous surfacing described, but it also serves to cement or adhere the surface and adjacent fibers of the sheet down in place and to one another. There is thereby provided a unitary surface on the sheet and at the same time a water resistant and generally porous surfacing. This surface will readily-pass air under slight pressure and will with only the slight resistance, due to the ilneness of the porosity at the surface, pass water if under a slight pressure.

As an alternative for the preparation of the form lining board as just above described, and preferred rather thanstoving in producing such form liner board; the following procedure which arrives at the same final result may be followed. In lieu of stoving the sheet after the application of surface coating asphalt to a prehot rolled or` natural board, the sheet, carrying its surface coating may be run under a hot roll which is preferably heated to a temperature of about 350 to 650 F. and runs at a peripheral speed of about 20 to 30 feet per minute. The effect of running the treated sheet under the hot roll,

which is usually referred to as hot rolling or as ironing, is to drive the asphalt coating applied on the surface into the surface in the same manner as was above described in connection with the stoving of the coated sheet. The hot ironing immediately drives the surface coating of asphalt into the surface portion of the sheet, but it also has another effect in that it irons down and smooths the surface of the sheet combining the smoothing and penetrating operations and it is for this reason that the hot rolling is preferable to the simple staving which does not provide the advantage of smoothing and ironing the surface of the sheet. For prehot-rolling the board surface is preferably slightly moistened.

In order to maintain the desired maximum surface porosity of the'form lining it is desired that the surface coating, such as asphalt, applied,

shall be held to a minimum. Fiber boards, a surface of which has been smoothed by prehotrolling in accordance with the procedure elsewhere herein described can be uniformily coated by the application of from 15 to 20 lbs. of asphalt per thousand sq.ft. of surfacing, or if the prehotrolling has resulted in a good smooth surface 10 to 15 lbs. of asphalt vper thousand sq. ft. will be suflcient, particularly if the board is finally rei hot rolled. Fiber boards which have not been hot rolled, that is, those which have their normal surface usually require the use of asphalt in the amount of between 20 to 30 lbs. per thousand sq. ft. of surface for a uniform minimum coverage, but if the board is rehot rolled an asphalt coverage from 15 to 25 lbs. per thousand sq. ft. will be sufficient. Starting with the same fiber board,'coverage in the amounts as just above set out result in a final surface permeability.

As an alternative method for applying the surface coating and one which eliminates what will now be referred to as rehot rolling, or stoving to effect the desired penetration of the asphalt applied, into the surface of the ilber board there may be added to the asphalt small percentages of materials which have the effect of increasing the penetration of the asphalt as it is applied. If there is added to the asphalt small amount of Hercolyn or Abalyn, which are methyl abietate, the enect at the rolls where the application of the asphalt is made will be substantially similar to the effect obtained through rehot rolling or stoving of the sheet after the asphalt has been applied. Since the ability of the asphalt to penetrate has been increased by the use of the materials mentioned, the asphalt will when applied at the rolls, if roller coated, penetrate into the surface of the ilber board sheet to which it is applied, with substantially the same effect as is obtained by rehot rolling or stoving the sheet after the application of asphalt to which such additional materials have not been added.

Heretofore there has been described several phases in the method of preparing form lining board which is used in connection with the inventions hereof and in addition there has been mentioned alternative procedures for the preparation of this product. It is of course, to be understood that the foregoing description while including a description of the various phases of the method of producing, is to be taken only as a specific exempliflcation' of the invention and that the procedures involved are quite broadly applicable and may be so utilized. Instead of the asphalt used for preparing the surface of the form lining board, other substances may be used, as for example, asphalt cut backs, emulsions, hard waxes, latex, resins, drying oils, varnishes and other equivalents or solutions or emulsions thereof, as will be readily understood by those skilled.

in the art to which these inventions relate.

It is believed that it will be clear from the foregoing that regardless of the particular substance which is used to provide the surface treatment, that it is the object to and that the such material should be so applied that the resulting form'liner board shall have a surface which is i'lnely porous, water resistant and in which the bers at the surface are bonded. Hard waxes such as paraffin and various resins may be applied in substantially the same manner as the asphalt was described as applied. Latex and some of the resins are probably best applied as a solution, that is, either actually dissolved in a solvent or possibly in the form of an emulsion. Drying oils, such as tung oil, linseed oil, soya bean oil and the like, may be applied by spray or roller or other suitable application, preferably with an accelerator to bring about the desired polymerization or oxidation upon subjection of the coated sheet to suitable heating or baking.

With respect to the use of the substances above mentioned, generally it must be definitely kept in mind that the surfacing materials useable do not necessarily include every substance comprehended within the various classifications mentioned. The substance used for surfacing should be limited to one which is not sticky or distinctly soft at thetemperatures at which the form lining is normally used, nor should it be excessively hard and brittle so that the coating applied at the surface of the form lining will crack or shatter under normal use at usual outdoor temperatures. Further, the treated surface of the form lining should preferably be substantially neutral. 'I'hat ls, it is preferably to be held Within the limits of pH 6 to pH 8, with however, reasonable variation from these limiting figures permissible, since form liner board prepared in accordance with the above description and having a pH at the treated surface of about pH 4.1 has in use produced on Athe surface of concrete cast thereagainst a surface considered satisfactory and a very distinct improvement over surfaces cast against other types of the usual materials used for form lining, though a better and harder surface will result at the preferred 6.0 to 8.0 pH range.

T'he above limitations concerning the acidity and alkalinity at the surface of the form lining board are preferred, due to the fact that if the surface against which the concrete is cast is excessively acid, that apparently right at the surfaces there ls a very thin layer of the concrete the setting of which is decidedly retarded so that when the form liner board is stripped, this very thin layer of unset powdery cement is removed with the form liner board. On the other hand, if ythe surface o1' the form liner board is excessively alkaline, the integral waterproofness of the form lining may be destroyed and the advantages gained by the use of a neutral strengthening treatment would not be realized.

In the foregoing there have been described the various treatments to which a fiber insulation board may be subjected toprepare it for use as concrete form lining. The preferred form of the invention incorporating the foregoing described principles and the preferred form of the concrete form lining hereof are as follows: A surface strengthening treatment such as has been described is used and is applied to a surface of the normal flber insulation board and the wetting agent treatment is applied as a final treatment after the surface strengthening treatment. the surface strengthening treatment preferably being a treatment with asphalt rehot rolled into the board surface. The fiber insulation board to be used is preferably Celotex cane ber insulation board sized with rosin and alum and of preferably a density of about 0.210 to 0.220 which preferably should have an air permeability of about 3 to 4 seconds per 100 cc. There is applied preferably to the bottom face of such fiber board a surface strengthening application -of asphalt of M. P. applied substantially uniformly over the surface at the rate of 15 to 20 lbs. per thousand sq. ft. of surface. The surface to which the asphalt has been applied is then subjected to a rehot rolling at a temperature of about 450 to 650 F. at the roll surface, which rehot rolling serves to drive the asphalt into the surface of the board and which to some extent causes a slight increase in the density of the board and some increase in the air resistance of the board. Should the processing be varied so that the asphalt coated sheet is subject to stoving to cause the asphalt to sink into the surface, the application of asphalt should preferably be at the rate from about 20 to 30 lbs. per thousand sq. ft. On boards prehereof, will therefore not be herein discussed in.

f .14 of other drying or vegetable oils of this same general character, but however, this phase of the general inventions involved, since such 'is con-- sidered to be an invention separate from those further detail. p

For certain usages it is conceivable that it may be desirable to use a surface strengthening agent which is not neutral but which is distinctly acid in nature to stillfurther facilitate stripping of a surface which will have the preferred absorption time of 1 to 45 minutes it has been found that a. surface tension reducing agent iapplied in the proper quantity as for example, a solution of sulphonated castor oil 6% by volume, applied at the rate of 1 to 3 gallons per thousand sq. ft. of surface will result in the desired water absorption time for the surface of the stoved product, whereas. in connection with the rehot rolled product a like coverage with a solution, of sulphonated castor oil 10 to 20% by volume, is required. Such application of the wetting agent reduces the water absorption time from substantially innite to that desired, that is, to about 1 to 45 minutes.I

The treatments `to which the sheet is subjected cause some increase in the density and ordinarily if a ber board of a density of 0.210 to 0.220 is used as the base material the finished product will, due to the rehot rolling and other treatment to which it has been subject have a nal density of about 0.250 to 0.270. With the treatments as have just been described, the ber board sheet which originally had a preferred air permeability of about 3 to 4 seconds, increase, due to the treatments to which the boards have been subjected. to an air permeability of about 6 to 12 seconds although an air permeability of up to about 20 seconds is allowable.

In the above descriptionit is of course to be understood that in connection with the preceding teachings, allowance is to be made for permissible variation in the preferred treatment, for example, whereas the surface strengthening treatment has been generally described as treatment with asphalt, there may be substituted therefore equivalent treatments with various ofthe other surface strengthening materials which were mentioned; and whereas treatment for surface tension reduction has been described as one with sulphonated castor oil of a particular concentration, it is readily apparent that such treatment may be with a solution of a different concentration, for example, twice the amount of solution but of half the concentration, or the treatment may be an equivalent treatment with othere surface tension reducing agents as has been previously particularly pointed out.

In preparing a concrete form liner board of the general nature of that above herein described the surface strengthening treatment may be one of such a nature that it has inherent wetting the form lining from the cement. Surface finish lof the concrete would be somewhat sacrificed for the purpose of obtaining easier stripping. In

such cases it may be desirable to use an acid treat-v 15 ment or acid wetting agent subsequent to the'application of the surface strengthening treatment, Y

or the surface strengthening treatment itself may vbe one wherein the material applied ,has an acid reaction. By the selection of a proper surface strengthening agent, of an acid character, the desired result may be accomplished without a subsequent treatment for acidifying and it is possible to obtain the desired water absorption rate by selection of the surface strengthening agent. Soya bean oil is satisfactory for this usage since due to the free fatty acids contained and developed during the polymerization thereof it has been found to produce such results. Other oils containing free fatty acids might (also be 'used in similar manner to obtain a like desired result. While above there have been mentioned two ways in which the surface tension depressant may be added, it has been found that the surface tension depressant may be added by other procedures. The surface tension depressant if miscible with the surface treating material may be mixed therewith and applied to the surface of the board as a single application. It is, of course understood by those skilled in the art that the sur- 40 face tension depressingiagent need not necessarily be a single and specific surface tension depressant, since equal effect can be obtained by using a mixture of several surface tension depressant agents. 0f course, in any case it is to be under- 45 stood that the surface tension depressant agent the principal reasons for the application of the properties in addition to its surface strengthenn ing properties and in such case the application of the wetting agent may be entirely eliminated or at least the concentration of the wetting agent which is applied may be very materially reduced, as may be required under the circumstances involved, to' obtain the desired water absorption rate of 1 to 45 minutes or up to the maximum rate of about minutes. It has been found for instance that claried raw soya bean oil has such properties and boards treated with soya oil and partially polymerized by baking will have an absorption time of from 10 to 15 minutes and may be used without further treatment. This is true surface treatment, as has been described, is to obtain the proper degree of surface strength and porosity of the finished product, it consequently follows that the quantity of the surface treat- 60 ing material used will at times need to be varied within reasonable limitations from the amount given in the specific example above. The finished product should have a. surface porosity and water absorption such that it will, at least at 24 hours after the rform liner has been manufactured, withon the surface, as meaning above the surface.

` wir This coating or 'surfacing of the form liner board of this inventionl'is not on but is in the sinface of the ber board, that is, by the treatment as it is carried out, the surface treating material is caused to largely sink into the surface of the board, the greater part of'it being present as surface coatings about the surfaces of the individual fibers at the board surface. The phrases just heretofore abovey referred to and other like phrases which may be used in thespeciflcation, it is to be understood are used in a limited sense, or otherwise, with the specific meaning as has just been pointed out in detail. i

When concrete is placed in a form lined with the above described form liner board, that portion thereof from the surface downward is under a certain amount of hydrostatic pressure depending upon the distance measured downwardly from the surface. Due -to this hydrostatic pressure, air, which may be at and adjacent to the surface between the form liner board and the concrete mass is forced into and passes through the inely porous surface of the form liner board, but it is believed that this surface momentarily resists the water flow, but however, upon the release of some of the pressure existing due to the escape of the trapped air, the water at and adjacent the surface begins to flow through the finely porous surface of the form liner board to be absorbed into the body thereof.

This flow of water apparently allows the es-V cape, from the concrete at an adjacent its face, of the water present in? excess, or at least a part of the excess of the water present and not required for proper hydration of the cement. This ilow of water apparently tends to cause the cement fines, which are adjacent to the surface, to be carried to the surface to ll voids between the surface particles and excess water which is ordinarily present as films between particles of the mix is largely removed and the particles are thus more closely compacted with the result that, due to these effects the face of the concrete which has been cast against the form liner board, when it hardens is more dense and harder at its surfacev than if cast against other forms of form lining. Due to the fact that substantially all the air trapped, or present at and adjacent the surface of the concrete mass, escapes into the form liner board, the resultant concrete is entirely or almost entirely free of the air pockets, aggregate pockets, bug holes and the like, which are common at the lsurface of concrete cast against other materials as form lining.

It is of course to be understood that the ooncrete mass which is cast against the concrete 'form lining is suitably tamped or vibrated as is preferably of wood or the ,like should be carefully inserted under an edge of the form liner board, whereupon after an edge has been loosened the form liner board may be peeled from the face of the concrete. In general there is sufilcient adhesion between the form liner board and the concrete to hold the liner board on the surface of the concrete, but not sufficient to prevent the ready peeling of the sheet from the surface. The resulting surface of the concrete will be found to be .uniform and dense and without substantial imperfections and `particularly there will not be visible on the face of the concrete, wood grain pattern marks or the like which may commonly be'noted when other forms of form lining have been used.

It has been mentioned that the desired surface against which the concrete is to be cast can be formed on a ilber board sheet which has not been sized and it was further pointed out that such. while it would produce the desired surface on the concrete, might be quite unsatisfactory from the standpoint of its use. As an alternative to the use oi either an unsized fiber insulation board or a sized fiber insulation board, the surface may be provided on a composite board which is dlagrammatically illustrated in Figure 3 of the drawings. In this illustration there is represented a finished product of about one-half inch thickness, which product is a composite of two separate sheets, one of which, the face sheet, is designated by the numeral 20, whereas the other, the back or base sheet, is designated by the numeral 2l. The face sheet 20, is a sheet of fiber insulation board, as has been described, which is one-sixteenth of an inch thick, more or less, although from the viewpoint of manufacture it is preferred that such sheet be approximately one-fourth inch in thickness, this being a ber insulation board sheet which has not been waterproofed with a rosin and alum size or the like. The base sheet 2i, is a sheet of fiber insulation board which has been sized with a. rosin and alum size or the like, and its thickness is such common practice, but it of course must also be understood that this tamping or vibrating of the mass before it sets should not be done in a manner which will cause injury to the surface of the form liner board, that is, if a vibrator is used it should be kept back from the surface say not less than about six inches and the vibrating member should not under any circumstances be allowed to contact the surface of the form liner board After the concrete which has been cast against the form liner board hereof has set for a period of approximately 24 hours; and not more than 72 hours, the form should be removed and it will be found that in general the small nails with which the form liner board was secured to the forms will pull through the form liner board and that the form liner board will remain on the surface of the concrete. A tool'with a thin blade as to bring the composite thickness to a thickness of substantially one-half inch. These two sheets, 20 and 2|, may be secured together by suitable means, preferably by spot gluing with a waterproof adhesive.

In the preparation of this composite sheet for use as a form lining, the surface of the unsized sheet 20 is treated in accordance with the described process as has been above set out in detail, except that if the sheet is not sized, less surface tension reducing agent is required and consequently about one-half the amount as above stated should be used, although it is preferred that the solution shall be of about one-half the concentration, that is, there would be used on a sheet where the surfacing coating has been subjected to a rehot rolling operation preferably about two gallons of the surface tension reducing solution of a concentration of about 2% by volume when sulphonated castor oil is used as the surface tension reducing agent. This composite sheet handles in stripping about as satisfactorily as does the preferred form of the liner board as has been heretofore described, as the sized base sheet remains substantially unaffected by water absorbed from the concrete and the composite sheet can be handled.

While from the foregoing it might be considered that the inventions hereof are applicable only in connection with a form lining board one-half inch thick, such is not the case. The fiber board l? sheet used may be of any convenient thickness, one-half inch thick is most readily available commercially. The 'inventions hereof may be ape plied to iiber insulation board of any convenient thickness, say from one-fourth inch to threefourths inch, or thereabout.

While above it has been stated that form liner board prepared as above should absorb l/2 cc. of water applied locally, or as a puddle within a period of from 1 to 45 minutes, it is to be understood that this limitation is an approximate and is given particularly since these limiting figures are those set up in a specification which has been prepared to cover fiber board concrete form lin? ing. However, according to the experience it is preferred that the form liner board, after it is manufactured should be capable of absorbing the 1/2 cc. of water in not less than 20 seconds or more than 60 minutes and this is the preferred rate of absorption for the form liner board of this invention.

In connection with the preparation of alform lining board in accordance with the foregoing descriptions, any of the boards so prepared may be given a surface which will result in a nished concrete surface which is patterned. The various forms of the concrete form lining, as preferably the final step in their preparation, can be subjected to treatment under an. embossing roller having a pattern thereon and the surface of the concrete will be patterned` in accordance with the pattern embossed on the surface of the form lining board. In this connection it is preferable that the pattern which is embossed on the surface of the form lining should not contain any deep portions nor sharp edges nor reentrant portions, but other than this there is substantially no limitation to the pattern which may be employed in this connection.

The invention hereof having been above described in detail, there is claimed the following:

l. The method of providing at the surface of a fiber insulating board a surface inherently waterproof but highly and finely porous surface and comprising the steps of applying to the surface of the board a thin and substantially waterproof coating of asphalt applied substantially uniformly at the rate of between about l to 30 lbs. per 1000 sq. ft., and heating the coating to the ternperature and for the length of time required for the applied surface coating to soften and to sink into the surface of the board to substantially coat the surface fiber thereof and to adhere together the surface and adjacent bers of the board,

the board thereby provided with an inherently,V

waterproof surfacing which is highly but finely porous to the passage of air and water therethrough.

2. The method of preparing a concrete form lining material comprising the step of applying to a surface of an air porous and water absorbent board form material an asphaltic material of about 180 F. M. P. in the amount of about 10 to 30 lbs. per 1000 sq. ft., the so treated material then hot rolled at a temperature from about 350 to 650 F. and the application to the treated surface of a surface tension reducing agent in an amount equivalent to between one to three gallons of a solution of between about 6 izo-18%, by volume, of sulphonated castor oil.

3. The method of preparing a concrete form lining material comprising the steps of applying at a surface of an air porous and water absorbent fiber insulating board, integrally waterproofed, a porous coating having substantially uniformly dis- 18 tributed porosity to' quently applying over, such porous coating atthe surface of the board a surface tension reducing agent. 4. 'Ihe method of preparing a, vconcrete fo lining sheet wherein, to a base material, a sheet of fiber insulation board composed largely of cellulose and integrally sized, there is applied to and adjacent a surface thereof asurface tension reducing agent, and at which surface there is applied a coating of thermo-plastic which is inherently waterproof; the coating is heated and sinks into the surface substantially coating the surface fibers and adhering the surface bers together at their points of contact providing a surfacing which is waterproof and is finely porous.

5. The method of manufacturing a concrete 'form lining wherein to an integrally sized base sheet of fiber insulation board, composed largely of cellulose, there is applied to that portion of the base sheet at and adjacent a surface thereof a wetting agent serving to increase the ability of the base sheet. at such surface, for absorbing water and there is applied at the surface of increased water absorptivity an inherently waterproof surfacing which is porous.

6. A concrete form lining board comprising a fiber insulation board composed largely of coarse cellulose containing fibers and of afdensity of between about 0.2l0 to 0.270, the original surface of said fiber board having an air resistance of from about three to four seconds per cc., the board at and adjacent a surface of the board a wetting agent, equivalent in amount in surface tension reducing eect, to the application of about one to three gallons of 6% to 18%, by volume, solution of sulphonated castor oil, and a porous but inherently waterproof asphalt application, applied at the rate of about 10 to 30 lbs. per 100 sq. ft.. at the wetted surfacefthe said surface being an ironed surface.

7. A concrete form lining board comprising a fiber insulation board composed largely of cellulose containing bers and of a density of between about 0.210 to 0.270, the original surface of said fiber board having an air resistance of from about three to fifteen seconds per 100 cc., at and adjacent a surface of the board a content of a wetting agent and a porous but inherently Waterproof asphalt application, at the wetted surface, applied at the rate of about l0 to 30 lbs. per 1000 sq. ft., the said surface being an ironed surface.

8. A concrete form lining board comprising a fiber insulation .board composed largely of cellulose, the bers at a face of the board adhered one to another by a waterproof adhesive, the amount of adhesive suicient to only thinly coat and to bond the surface bers and adjacent bers together at their points of contact with one another but insuilicient to close the surface porosity of the ber board whereby the ability of the treated surface to pass air and Water, although reduced somewhat is retained, the board at said treated face thereof having an ironed surface produced by ironing at a temperature of between about 350 to 650 F.

9. A concrete form lining board comprising as a base thereof a coarse flbered ber insulation board, the bers thereof at and adjacent a surface thereof adhered at their points of contact one with another and the fibers at said surface thinly coated with a. waterproof cementing substance, the original surface vpores of such board substantially unreduced in number but reduced in size by the coating of waterproof cementing substances air and water, and subse- 19 on the surfaces of the surface bers, the such thinly coated and 4adhered bers comprising merely a surface layer and the body of the ber board excepting for such `surface layer devoid of the waterproof cementing substance.

10. A concrete form lining comprising a base sheet of water absorbing material having applied at a surface thereof a porous inherently waterproof coating having per unit of area a rate of transmission of watertherethrou'gh lower than the rate of absorption of water from a surface of the base sheet, the sheet excepting for such surface coating devoid of the inherently waterproof coating material.

' 11. An article of manufacture comprising a concrete form lining board, the board comprisinga felted ber sheet having porosity to water and air, a water tension reducing agent carried by the bers of such sheet at a surface and inwardly therefrom and a coating at such surface, the coating as such inherently resistant to the penetration of water, the such coating having porosity therethrough capable of passing in not exceeding 60 minutes 1/2 cc. of water applied locally to the surface and providing at the surface of the ber sheet a surfacing coating inherently waterproof but penetrable by water within the limitation of the Water transmitting capacity of the porous sur facing coating.

12. An article of manufacture comprising a concrete form lining board, the form lining board being of compound construction and from an intermediate plane thereof in opposite directions comprising board form layers not less than 11g" thick, one layer comprising a felted ber sheet lthe bers of which carry a surface tension reducing agent, the other layer comprising a sheet resistant to the softening effect of moisture, the two sheets secured together in face to face relation and comprising a,unitary article.

13. An article of manufacture comprising a concrete form lining board, the form lining boardv being of compound construction and from an intermediate plane thereof in opposite directions comprising felted ber sheets, one relative to the other, waterproofed and resistant t' absorption of water. the relatively water absorbent felted ber sheet having at a face thereof a porous, air and water permeable layer of a waterproof material.

y 14. The method of controlling the rate of ab- Ksorption of water by a water absorbing base sheet and comprising the steps; applying at a surface of the base sheet a coating of predetermined porosity to pass water at a, rate per unit area less 'than the rate at` which the base sheet is capable of absorbing Water per unit of surface area of a surface of the base sheet, confining water as a constituent of concrete mix and under a hydrostatic head at and adjacent the coated face of the base sheet, whereby due to the hydrostatic pressure the water passes through the coating of predetermined porosity at a rate controlled bythe limiting factor of the rate at which Water may pass through the porous coating.

15. A mold form' member for molding poured hydraulic-setting mixes of concrete'and the like, comprising a Water absorptive articial board of felted ber, a waterproof coating on the surfaces of the surface bers ofthe board and adhesively bonding such surface bers one to another and to adjacent bers at their points of contact and providing a porous waterproof surface with pores from the interior of the board opening through the porous waterproof surface, said porous waterproof surface on the board serving to prevent bonding of the bers to the set hydraulic material, and a wetting agent available at the surface of the board, said wetting agent being effective upon contact with the poured mix to facilitate the rapid entry of water and escape of entrapped air from the mix into the board through the porous waterproof surface on the board.

16. A mold form member for molding poured hydraulic-setting mixes of concrete and the like. and having at a surface a porous coating permeable to air and water and of predetermined porosity to serve to limit the maximum rate of the passage of air and water through such porous coating and away from the mass molded thereagainst and comprising, a water-absorptive artificial board of felted ber, an asphaltic coating on the surfaces of the surface bers of the board and adhesively bonding such surface bers one to another and adjacent bers at their points of contact, the porosity of such coating being a predetermined porosity serving as a limiting factor to limit the rate of passage of Water and air therethrough in unit time to a predetermined quantity, the mold form member having pores extending from the interior thereof and opening .through the DOIOUS asphaltic surface, and a wetting agent available at the surface of the board, said agent being effective upon contact with the poured mix to facilitate the rapid entry of Water and escape of entrapped air from the mix into the board through the porous waterproof surface on the board.

EMILE FREDERICK, JR. WALLACE WATERFALL.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 1,920,065 Davis July 25, 1933 1,941,769 Ward Jan, 2, 1934 2,073,894 Wood Mar. 16, 1937 2,176,981 Smith et al. Oct. 24, 1939 2,208,236 Wiener July 16, 1940 1,532,084 Shaw Mar. 31, 1925 1,937,306 Barriball Nov. 28, 1933 1,937,993 Stees Dec. 5, 1933 1,899,535 Teague Feb. 28, 1933 2,168,286 Eustis Aug. 1, 1939 1,956,866 Keller May 1, 1934 1,465,541 Brown Aug. 21, 1923 2,296,553 Heritage et al Sept. 22, 1942 2,298,579 Meyer Oct. 13, 1942 1,818,874 Ulrich Aug. 11, 1931 1,995,623 Richter (1) Mar. 26, 1935 2,103,640 Richter (2) Dec. 28, 1937 2,274,792 Jennings Mar. 3, 1942 OTHER REFERENCES Engineering News-Record, Dec. 18, 1941, article page 72, Absorptive Form Lining Tests at Friant. 

